Battery powered charger

ABSTRACT

A charger for recharging the batteries of a portable electronic device even when no external power source is available. A battery or cell is installed within the charger, and when no access is available to a fixed power source into which the charger can be plugged, the internal battery or cell can be used to recharge the electronic device. The internal battery can be a primary battery or a secondary battery. In the latter case, the internal battery can be maintained in a charged state by means of circuitry which, when the charger is plugged into the external power source, charges the internal battery as well as the battery of the electronic device. The external power source can be either an AC power wall socket, in which case the charger includes AC/DC voltage conversion circuits, or a car lighter socket, or the DC output of a conventional wall charger.

RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 12/520,093, entitled“Battery Powered Charger”, which was filed as a §371 ofPCT/IL2007/001582, which was filed on Dec. 20, 2007 claiming priorityfrom U.S. Ser. No. 60/875,814 and U.S. Ser. No. 60/996,220, which werefiled Dec. 20, 2006 and Nov. 7, 2006, respectively. The contents ofthese applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to the field of charging devices forportable electronic equipment, especially those for use with mobiletelephones.

BACKGROUND OF THE INVENTION

Portable electronic devices generally use internal rechargeablebatteries for operation. In order to maintain the internal batteries ina state of charge, the device is generally recharged at regularintervals using a wall mains adaptor unit, whose function is to convertthe comparatively high voltage AC mains voltage available at wallsockets, to a low voltage suitable for inputting to the device'scharging input. At the same time, such a wall charger often regulatesthe charging profile to the internal batteries of the electronic device,in order to maximize charging efficiency, and to ensure safe charging.Other types of charger unit utilize the low voltage DC power sourceavailable in automobiles, such as the cigarette lighter socket, in orderto charge the device's internal batteries. Such external power sourceswill be known as fixed power sources in this application. Furthermore,the term “wall charger” will generally be used in this application toinclude any type of charger which is generally plugged into a fixedpower source.

However, an AC mains power source, or a car lighter socket, is notalways available when the battery of the portable device requirescharging, and the user then has to either carry with him spare chargedbatteries, which could be a safety hazard, or must purchase suchbatteries, which is not always a simple task, as many portable devices,and especially mobile phones, use dedicated battery packs which are notwidely available. Even then, such battery packs are often supplied in anon-charged state.

One solution to this problem is described in U.S. Pat. No. 6,479,963,for “Rechargeable Battery Packs”, to the inventors of the presentapplication, in which a novel battery pack is disclosed which can befitted with a widely available primary cell to recharge the rechargeablecells of the portable device. Another solution is described inco-pending PCT Application published as International Patent ApplicationNo. WO/2006/095353 for “Portable Battery Operated Power Supply”, also toinventors of the present application, in which a special externalbattery pack, preferably containing a rechargeable cell, is used toenable recharging of the device at any location.

Each of these solutions has its own disadvantage. The former requiresthat the device be equipped with the special battery pack such as thatdescribed in the patent, while the latter requires of the device ownerto carry with him/her the special external battery pack, and to ensurethat the external battery pack is kept charged by connecting it to aconventional wall charger at the required intervals.

There therefore exists a need for a portable charging system whichovercomes at least some of the disadvantages of prior art systems andmethods, to enable the user of portable electronic devices to simplyrecharge the internal batteries of the device, without the need to haveaccess to a fixed source of charging power.

Though the term battery is strictly speaking understood to mean a packof at least two cells, in common usage the term is also understood tomean a single cell. Consequently, these two terms, battery and cell, mayhave been used interchangeably in this application, and may also havebeen thuswise claimed, and the number of cells in the device of theinvention is not meant to be limited by use of one or the other term.

The disclosures of each of the publications mentioned in this sectionand in other sections of the specification, are hereby incorporated byreference, each in its entirety.

SUMMARY OF THE INVENTION

The present invention seeks to provide a new device for providing powerto a portable electronic device, either for powering the portableelectronic device, or for recharging the batteries of the portableelectronic device when no access to an external fixed power source isavailable. The invention is based on the use of an external charger,such as a wall charger, with an associated auxiliary battery or cell,such that when no access is available to a fixed power source into whichthe external charger can be plugged, such as a wall power point, or acar lighter socket, the associated auxiliary battery or cell can be usedto recharge the battery of the electronic device. The charging device ofthe present invention preferably incorporates charge control andconversion circuitry for converting the input voltage supplied from theexternal source to that required to charge the associated auxiliarybattery or cell, and to that required for input to the external chargerinput socket of the electronic device, for powering the electronicdevice or for charging the electronic device's internal battery. Thecharge control and converter circuit is preferably a bidirectionalconverter, in order to control both the charging current from theexternal source into the associated auxiliary battery, and to controlthe discharge current from the associated auxiliary battery into theportable electronic device. The circuitry of the battery powered chargerof the present invention differs from that of prior art multi-sourcechargers, such as that described in U.S. Pat. No. 7,166,987 to K. S. Leeet al, for “Portable Charger for Mobile Phone”, in that the use of asingle bi-directional DC/DC converter as the charge controller for theauxiliary battery enables the provision of a simpler charger structure.The DC output from the external source, whether directly from a carsocket, or from an AC/DC wall charger, can be at such a voltage levelthat it can be supplied directly to the mobile electronic device powerinput socket, or, by means of a single bi-directional DC/DC voltageconverter, to the auxiliary battery. This same DC/DC converter, byvirtue of its bidirectionality, is able also to handle, when required,the flow of current and the voltage conversion from the battery out tothe mobile device, such that effectively all of the charge control andconversion functions are performed with a single bidirectional controlcircuit.

The charge control circuit also preferably incorporates batterychemistry detection circuitry, such as that described in co-pendingInternational Patent Application PCT/IL2007/001532 for “Charging Methodsfor Battery Powered Devices”, or in similar battery chemistry detectioncircuits with simpler algorithms, as is known in the art, such that ifthe associated auxiliary battery or cell is detected as being primary,recharging thereof is disenabled. This feature is even more important ina battery powered wall charger than in a conventional battery charger,since the additional heat generated in a battery powered wall chargerwhen operating, increases the internal temperature, and the possibilitythat a primary cell being charged therein may fail catastrophically

According to a first preferred embodiment, the auxiliary battery or cellis installed within the external charger itself, preferably within adedicated battery cavity. An advantage of this embodiment over the priorart devices described hereinabove is that the electronic device usergenerally carries a normal wall charger, to enable the electronic deviceto be charged in the conventional manner. Therefore, the use of thecharger of this embodiment of the present invention, while providing theuser with an in-the-field charging capability, does not involve the needto carry any additional equipment which the user would not otherwisehave to carry with him/her.

According to a second preferred embodiment of the present invention, theassociated auxiliary battery or cell and its charge control circuitryare not housed within the external charger unit itself, but arecontained within a separate housing, which can be connected to aconventional external charger by means of a flying lead. Connection tothe portable electronic device is performed in the usual manner, throughthe charging input socket of the device, either by means of a plug, orby means of another flying lead. This embodiment differs from the firstembodiment in that the auxiliary battery is housed in a compartmentseparate from that of the external charger circuits. In that respect,the external charger output can be considered as being equivalent to thewall source of power, or to the car lighter socket source of power.

The auxiliary battery of the wall charger of the present invention maybe either a primary cell, which is readily available from numeroussources for replacement when expended, or a rechargeable cell, in whichcase, the charger circuits can be arranged such that, once the presenceof a secondary cell has been detected, the cell is maintained ready foruse in a charged condition, either by being charged if necessary, or bybeing just trickle charged if already essentially fully charged, everytime that the wall charger is connected to the fixed power source.

According to a further preferred embodiment of the present invention,the presence of a battery in the charger provides it with an advantageover conventional chargers, in enabling easier compliance with thecurrent policy of reducing “stand-by power” of electronic devices. Ifthe associated battery is fully charged, the circuitry of the charger ofthe present invention need only be powered up when there is need toprovide power to the portable electronic device. The presence of theon-board battery enables the charging circuits of the charger to becompletely disconnected from the external source, such that no stand-bypower at all is used from the wall socket or from the car socket. Theinternal battery can be used to power a very low-power detection circuitfor monitoring the portable electronic device for renewed power demand.Once such a demand is detected, the charging circuits can be reconnectedto the external source, and can draw power from the external source asneeded. This is in contrast to conventional chargers, which generallyhave to be left connected in a stand-by status to the external source,drawing a trickle charge current whose need may not be immediate, butwhich consumes typically 250 mW for a small wall charger unit typicallyof the order of 5 Watts or less. Additionally, the detection circuitscan also monitor the state of charge of the on-board charger battery,either by means of its terminal voltage, or by the elapsed time sincethe last charging operation, and can then reconnect the external sourcewhen the state of charge falls below a predetermined level, regardlessof whether the electronic device has demanded current or not. This thenensures that the internal battery of the charger remains charged evenwhen the charger is in stand-by mode.

The circuits of the wall charger of the present invention are generallymultifunctional and bidirectional, in that they have to be capable ofperforming at least some of the following functions:

-   (i) When the charger is plugged into a fixed power source, whether    an AC wall power source, or a car socket, or the DC output of a    conventional wall charger unit, the circuits should preferably    convert the voltage up or down, depending on the voltage supplied,    and the voltage required, to a suitable level to provide current for    charging or powering the electronic device when it is attached.-   (ii) When the charger is plugged into a fixed power source, (as    described above) the circuits should be able to convert the voltage    to a suitable level to provide current for charging the auxiliary    battery or cell of the wall charger.-   (iii) The circuits should preferably ascertain whether the auxiliary    battery or cell of the wall charger is primary or secondary, so that    if primary, the internal battery charging circuit is not enabled.-   (iv) When an electronic device is attached to the wall charger, and    the charger is not connected to a fixed power source, the circuits    should enable the device to draw charging current from the auxiliary    battery, whether primary or secondary.-   (v) Since the wall charger auxiliary battery, if a secondary    battery, needs to be both charged and discharged, the circuitry    which controls these functions preferably has bidirectional    characteristics, such as is described in PCT Application No.    PCT/IL2006/000317, published as International Patent Application No.    WO/2006/095352 for Bidirectional Battery Charge Controller,    incorporated herein by reference in its entirety. If the wall    charger is intended for use only with a primary battery, then    bidirectionality is not required.

There is thus provided in accordance with a preferred embodiment of thepresent invention, a charger for a battery operated electronic device,the charger comprising:

-   (i) an input for connection to an external power source supplying    current at a first voltage,-   (ii) an output for connection to the battery operated electronic    device,-   (iii) circuitry for supplying the electronic device with current    when the charger is connected to the external source,-   (iv) a cavity for mounting in the charger at least one battery    having a terminal voltage different from the first voltage, and    different from the voltage required for inputting to the electronic    device, the battery supplying the electronic device with current    when the charger is not connected to the external power source,-   (v) a bidirectional converter and charge controller adapted to    control current supplied from the at least one battery mounted in    the charger to the electronic device, and to control current flowing    into the at least one battery when the charger is connected to the    external power source, and-   (vi) circuitry for detecting the chemistry of the at least one    battery.

In the above described charger, the bidirectional converter and chargecontroller may preferably be further adapted to convert the firstvoltage to a voltage suitable for charging the at least one battery, andto convert the terminal voltage to a voltage suitable for inputting tothe electronic device. Additionally, the external power source cansimultaneously cause current to charge the at least one battery, and tosupply the electronic device with current. Furthermore, the currentsupplied by the charger to the electronic device may preferably beutilized to perform at least one of operating the electronic device andcharging the battery of the electronic device.

There is further provided in accordance with yet another preferredembodiment of the present invention, a charger as described above,wherein the converter and charge control circuit further comprisescircuitry to prevent supply of charging current to the at least onebattery when the charger is connected to the external power source.

In accordance with still another preferred embodiment of the presentinvention, the circuitry for detecting the chemistry of the at least onebattery may preferably be adapted to prevent supply of charging currentto the at least one battery when the battery chemistry detectioncircuitry determines that the at least one battery is a primary battery.In all of the above charger embodiments, the at least one batterymounted within the charger is preferably replaceably mounted.Additionally, the charger may further comprise conversion circuitry forconverting the voltage of the external power source to that suitable forinputting to the electronic device.

In connection with the above described chargers, the external powersource may preferably be either an AC mains power source, or the lowvoltage DC output of a conventional wall charger, or the output of a carlighter socket.

There is further provided in accordance with still another preferredembodiment of the present invention, a charger for a battery operatedelectronic device, comprising:

-   (i) an input for connection to an external power source,-   (ii) an output for connection to the battery operated electronic    device,-   (iii) a cavity for mounting at least one battery within the charger    which can supply the electronic device with current when the charger    is not connected to the external power source: and-   (iv) control circuitry powered by the at least one battery, for    disconnecting the charger from the external source when the at least    one battery is fully charged and when the electronic device is not    drawing current from the charger.

In such a charger, the at least one battery may be either a primary or asecondary battery. Furthermore, the control circuit may preferably beadapted to monitor the current drawn by the portable electronic device,and to reconnect the charger to the external source when such currentdemand exceeds a predetermined level, or to monitor the state of chargeof the at least one battery, and to reconnect the charger to theexternal source when the state of charge falls below a predeterminedlevel. In the latter case, the state of charge is monitored bymonitoring at least one of the terminal voltage of the at least onebattery, and the elapsed time since the at least one battery wascharged. Finally, in such chargers, the external source may preferablybe the mains supply, and disconnection of the charger from the externalsource essentially eliminates the stand-by current drawn from the mainssupply.

In any of the above described charger embodiments, the charger maypreferably be in a physically separate housing from the electronicdevice.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully fromthe following detailed description, taken in conjunction with thedrawings in which:

FIG. 1 illustrates schematically a wall charger, constructed andoperative according to a first preferred embodiment of the presentinvention, and its connection to a portable electronic device;

FIG. 2 is a schematic block diagram showing one preferred embodiment ofthe internal circuitry of the wall charger of the present invention;

FIG. 3 illustrates schematically a wall charger, constructed andoperative according to a second preferred embodiment of the presentinvention, differing from that of FIG. 1 in that the auxiliary batteryis mounted in a housing separate from the external charger; and

FIG. 4 is a schematic block diagram showing a preferred embodiment ofthe internal circuitry of the battery powered charger of the embodimentof FIG. 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to FIG. 1, which illustrates schematically a wallcharger 10, constructed and operative according to a first preferredembodiment of the present invention, The wall charger preferably hasconventional power pins 12 for inserting into a wall socket (not shown),though it may also use a conventional plug on the end of a flying leadcable, or a push-in plug for use with a cigarette lighter socket in acar. A cable 13 provides connection to a mobile telephone 14, used as anexample of a portable electronic device which can be charged by the wallcharger. The output may equally well be provided in the form of a cradlein which the phone or other electronic device sits without a connectioncable. The wall charger 10 differs, however, from a conventional wallcharger in that it also contains a battery cavity 15, inside of whichcan be installed one or more cells or batteries 16, which are preferablysecondary. Alternatively and preferably, primary cells or batteries maybe used, this being understood to include a fuel cell also. The wallcharger can be used in the conventional manner, whereby the cable 13 isplugged into the charging socket 17 of the phone 14, and the phoneoperated or the internal battery of the phone charged from the fixedpower supply. At the same time that the wall charger is operating thephone or charging the phone's internal battery, it can also charge thewall charger internal battery 16, if it is a secondary battery, so as tomaintain it in a state of full charge. If it is desired to operate thephone or charge the phone battery in a situation where no fixed powersource is available into which to plug the wall charger, then the wallcharger is connected to the phone by means of its cable 13, or by meansof mounting into the charging cradle, and the phone is supplied withcurrent from the wall chargers internal battery 16. The internalcircuitry of the wall charger is preferably designed to prevent chargingof its internal battery 16 if it is a primary battery.

Reference is now made to FIG. 2, which is a schematic block diagramshowing one preferred embodiment of the internal circuitry of the wallcharger 10 of the present invention shown in FIG. 1. The comparativelyhigh AC mains voltage, input through the power pins 12 from the fixedpower source, is first preferably converted down to a comparatively lowDC voltage in the AC/DC converter circuit 20. This DC voltage ispreferably chosen to be suitable for direct application to the powerinput socket of the mobile device. In the case of a “wall charger” forplugging into an automobile cigarette lighter socket, the circuit 20would be a DC-DC converter, which converts the 12 V DC input from thecigarette lighter socket to a preferably lower DC voltage output for usedirectly at the input to the mobile device. In the case that theexternal source of power is a conventional wall charger which provides alow voltage DC output, the AC/DC converter circuitry 20 may be omittedsince the external power source contains these functions. This lastembodiment is described further in the embodiments of FIGS. 3 and 4. Theconverter circuit 20 is preferably configured as a current source, as isthe usual case in battery charging adapters, simply driving chargecurrent into the power input socket of the phone or other deviceconnected to the charging cable 13. A current sensing resistor 24preferably provides a feedback sense signal 21 to the AC/DC convertercircuit 20, to limit the charge current it can supply to the phone orother device.

The DC output of the converter circuit 20 is also preferably connectedto a bidirectional DC/DC converter and charge control circuit 22, whichis directly connected to the internal battery 16 of the wall charger.The bidirectional converter and charging circuit 22 controls the flow ofcharging current from the DC output of the AC/DC converter circuit 20,or from the DC power source when applicable, into the internal battery16 when the charger is plugged into the external power source, andconverts the voltage to that suitable for charging the internal battery16. The DC/DC converter preferably includes a battery chemistrydetection circuit 26, such that charging current can be disabled if thecircuit detects that the internal battery 16 is not a secondary battery,or is a secondary battery but is in a condition that indicates thatcharging would not be advised.

The DC/DC converter also controls the flow of charging current from theinternal battery 16 to the phone or other device through the chargingcable 13, when the charger is not plugged into the external powersource, and performs the voltage conversion to enable the internalbattery to power the mobile device. The bidirectional charge controlcircuit 22 is thus functional to fully control the flow of current intoand out of the internal battery 16 of the charger, and to convert thevoltages to levels suitable for charging the battery 16 or for poweringthe mobile device 14. An optional STATUS signal line 23 may preferablybe provided to notify the charge control and conversion circuit 22 whenthe wall charger is plugged into an external power source, so that itcan enable charging of the internal battery 16, but may disabledischarging thereof. This feature may be useful since the external powersource, when plugged in, can generally supply all of the currentrequired by the phone or other mobile device, and there may be no needto draw current from the internal battery. With or without the STATUSsignal input, the battery powered charger of the present invention alsodiffers from those generally described in the prior art, in that thecircuit arrangement of the present invention, when plugged into theexternal power source, is able to both recharge its own internal battery16, and to supply the phone or other mobile device 14 with current foroperating or for charging its own internal battery.

In embodiments of the charger which are intended only for use with aprimary battery, the bidirectional charging circuit 22 can be replacedby a unidirectional circuit which needs to control only the flow ofcharging current from the internal battery 16 out to the charging cable13.

Although for clarity, each of the circuit functions have beenschematically shown in FIG. 2 as separate blocks, it is to be understoodthat in practice, all or some of the functions may preferably beperformed by one multi-functional circuit.

Reference is now made to FIG. 3, which is a schematic illustration of afurther preferred embodiment of the battery powered charger 30 of thepresent invention. The charger contains an auxiliary battery or cell orcells 32, replaceable if needed, and charge control circuitry (not shownin FIG. 3) for controlling flow of current out of this battery or cellto the mobile telephone 14 (used as a non-limiting example of theportable electronic device), and into this battery or cell when chargedby the external source. This embodiment is thus similar in concept tothat shown in FIGS. 1 and 2, with the difference that in thisembodiment, use is made of a conventional wall charger 31, such as thatgenerally supplied with the phone 14, as the external power source. Thisconventional wall charger supplies a low DC voltage both for poweringthe mobile phone 14 or charging its internal battery, and for chargingthe auxiliary battery or cells 32 of the battery powered charger 30 ofthis embodiment. In the preferred example shown in FIG. 3, the batterypowered charger 30 contains two cells, but it could equally well containa single cell or battery, or more than two cells. The advantage of thisembodiment is that the battery powered charger 30 is then an independentunit, which can be provided as an optional accessory in addition to thenormal wall charger 31 of the device. The battery powered charger 30 ispreferably connected to the charging port 17 of the portable electronicdevice by means of a cable 33. In order to provide interchangeabilitywith the conventional charger 31, the plug 34 provided on the end ofthis cable is preferably of the same type as the plug 35 provided on theconventional wall charger of the electronic device. The conventionalwall charger can thus be used to power the phone or charge the phone'sinternal battery in one of two different modes; either with theconventional wall charger plugged directly into the phone, or with theconventional wall charger feeding the battery powered charger 30 of thisembodiment, which then operates in a feed through chargingconfiguration.

Reference is now made to FIG. 4, which is a schematic block diagramshowing one preferred embodiment of the internal circuitry of thebattery powered charger 30 of the embodiment of FIG. 3 of the presentinvention. The circuit structure is essentially similar to that of FIG.2 except that the AC/DC converter circuitry 20 of the embodiment of FIG.2 now preferably resides within the conventional wall charger 31 of FIG.3. The DC output current from the conventional wall charger 31 ispreferably input from its cable plug 35 through an input socket 36. Theconventional wall charger is preferably configured as a current source,as is the usual case in battery charging adapters, simply driving chargecurrent from the input socket 36, straight through the battery poweredcharger 30, and into the charging input socket 17 of the phone. Acurrent sensing resistor 44 may preferably be provided to supply afeedback sense signal 41 back to the conventional wall charger 31, tolimit the charge current it can supply to the phone.

The DC output of the conventional wall charger external power source isalso connected to a bidirectional DC/DC converter and charge controlcircuit 42, which is directly connected to the internal battery 32 ofthe battery powered charger. The DC/DC converter preferably includes abattery chemistry detection circuit 46, such that charging current canbe disabled if the circuit detects that the internal battery 32 is not asecondary battery, or is a secondary battery but is in a condition thatindicates that charging would not be advised. The bidirectionalconverter and charging circuit 42 controls the flow of charging currentfrom the input DC power source into the internal battery 32 when thebattery powered charger is connected to the conventional wall chargerexternal power source, and converts the voltage to that suitable forcharging the internal battery 32. It also controls the flow of chargingcurrent from the internal battery 32 to the phone or other devicethrough the charging cable 33, when the battery powered charger is notconnected to the conventional wall charger external power source, andperforms the voltage conversion to enable the internal battery to powerthe mobile device. The bidirectional charge controller 42 is thusfunctional to fully control the flow of current into and out of theinternal battery 32 of the battery powered charger, and to convert thevoltages to levels suitable for charging the battery 32 or for poweringthe mobile device 14. An optional STATUS signal line 43 may preferablybe provided to notify the charge control circuit 42 when the wallcharger is plugged into an external power source, so that it can enablecharging of the internal battery 16, but disables discharging thereof.

In embodiments of the charger which are intended only for use with aprimary battery, the bidirectional converter and charging circuit 42 canbe replaced by a unidirectional circuit which needs to control only theflow of charging current from the internal battery 32 out to thecharging cable 33.

It is appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the present inventionincludes both combinations and subcombinations of various featuresdescribed hereinabove as well as variations and modifications theretowhich would occur to a person of skill in the art upon reading the abovedescription and which are not in the prior art.

We claim:
 1. A charger for a battery operated electronic device, saidcharger comprising: an input for connection to an external power sourcesupplying current at a first voltage; an output for connection to saidbattery operated electronic device; circuitry for supplying saidelectronic device with current for charging or powering the electronicdevice when said charger is connected to said external source; a cavityfor mounting in said charger at least one battery having a terminalvoltage different from said first voltage, and different from thevoltage required for inputting to said electronic device, said batterysupplying said electronic device with current when said charger is notconnected to said external power source; and a bidirectional converterand charge controller for controlling current supplied from said atleast one battery mounted in said charger to said electronic device, andfor controlling current flowing into said at least one battery when saidcharger is connected to said external power source.
 2. A chargeraccording to claim 1 and wherein said bidirectional converter and chargecontroller is further adapted to convert said first voltage to a voltagesuitable for charging said at least one battery, and to convert saidterminal voltage to a voltage suitable for inputting to said electronicdevice.
 3. A charger according to claim 1, wherein said external powersource can simultaneously cause current to charge said at least onebattery, and to supply said electronic device.
 4. A charger according toclaim 1, and wherein said current supplied by said charger to saidelectronic device is utilized to perform at least one of operating saidelectronic device and charging the battery of said electronic device. 5.A charger according to claim 1, and wherein said converter and chargecontrol circuit further comprises circuitry to prevent supply ofcharging current to said at least one battery when said charger isconnected to said external power source.
 6. A charger according to claim1 and wherein said at least one battery mounted within said charger isreplaceably mounted.
 7. A charger according to claim 1, furthercomprising conversion circuitry for converting the voltage of saidexternal power source to that suitable for inputting to said electronicdevice.
 8. A charger according to claim 1 and wherein said externalpower source is an AC mains power source.
 9. A charger according toclaim 1 and wherein said external power source is the low voltage DCoutput of a conventional wall charger.
 10. A charger according to claim1 and wherein said external power source is the output of a car lightersocket.
 11. A charger according to claim 1 and wherein said charger isin a physically separate housing from said electronic device.